Player picks Opus when the browser can decode it and a sidecar exists (else lossless), injecting the sidecar before stream init; seek reuses the same format. Adds the Backfill-Opus bulk API endpoint + CMS action.
Retire the Tracks list view; promote the Releases view to /releases with
medium tabs (ALL/CUTS/SESSIONS/MIXES). Migrate bulk profile/high-res
backfill and per-track waveform columns into the releases grids. Point
catalogue cards at the three mediums. Remove dead BrowseMode/ViewModel.